1. Field of the Invention
The present invention relates to a bearing unit and a drive shaft assembly for driving wheels of an automobile (front wheels of FF vehicle, rear wheels of FR vehicle, or any wheels of 4WD vehicle).
2. Description of Related Art
As illustrated in FIG. 45, a drive shaft 1 for transmitting power from an engine to driving wheels connects a stationary constant velocity universal joint J1 on an out-board side (vehicle body side surface side with respect to vehicle width direction) and a slidable constant velocity universal joint J2 on an in-board side (vehicle body center side with respect to vehicle width direction) by an intermediate shaft 2. The constant velocity universal joint J1 on the out-board side is connected to a hub 4 rotatably supported by a wheel bearing 3, and the constant velocity universal joint J2 on the in-board side is connected to a differential 5.
The wheel bearing 3 includes a bearing inner ring 3a fixed to the outer periphery of the hub 4, a bearing outer ring 3b fixed to a knuckle member 6 extending from a suspension on the vehicle body side, and a plurality of rows of rolling elements 3c arranged between the bearing inner ring 3a and the bearing outer ring 3b. Usually, the bearing inner ring 3a is press-fitted onto the outer periphery of the hub 4, whereby the two components are fixed to each other. The bearing outer ring 3b is usually fixed to the knuckle member 6 by fixing a flange 3b1 of the bearing outer ring 3b to the knuckle member 6 by means of a bolt.
When assembling the conventional drive shaft 1 to the vehicle, in a state in which the hub 4 and the wheel bearing 3 are fixed to the knuckle member 6 in advance, the out-board side shaft end of the drive shaft 1 (stem portion 7a of outer joint member 7) is inserted into the inner periphery of the hub 4, and a nut 8 is screwed with the shaft end protruding from the hub 4 (see, for example, Patent Document 1). By fastening the nut 8, the entire drive shaft 1 slides to the out-board side, and a shoulder portion 7b of the outer joint member 7 is brought into contact with an end surface of the bearing inner ring 3a. With this structure, the outer joint member 7 and the hub 4 are positioned in an axial direction, and a predetermined pre-load is imparted to the wheel bearing 3. The outer peripheral surface of the stem portion 7a of the outer joint member 7 and the inner peripheral surface of the hub 4 are connected together by a spline (not shown), and the driving force of the engine transmitted to the outer joint member 7 is transmitted to the wheel via the spline and, further, the hub 4.    [Patent Document 1] JP 2004-270855 A